JPH0481579A - Scroll casing for water turbine - Google Patents

Abstract

PURPOSE:To facilitate manufacture by forming an outer plate, installed at the outside of an inner plate so as to surround this inner plate, into a scroll form so as to make a distance from a casing center axis become smaller successively in a range from the inlet side to a roll end part. CONSTITUTION:A section rectangular flow passage is formed by an inner plate 5 erected out of a speed ring 3, and outer plate of constant height H, installed at the outside of this inner plate 5 and so as to surround this inner plate, and an end plate 7 connecting both ends of the inner plate 5 and the outer plate 6. Then, the outer plate 6 is formed into a scroll form so as to make a distance from a casing center axis C become smaller successively in a range from the inlet side to the roll end part. With this constitution, these inner and outer plates 5, 6 are formed into a flat plate form, whereby only the outer plate 6 is good to be formed into a scroll form, so that its manufacture can be done easily.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a volute casing for a water turbine.

In general, the spiral casing of a water turbine has a circular flow path cross-section, as shown in Figure 3, and a roughly cylindrical tube divided into multiple pieces, as shown in Figure 4. 1a, lb・
... are successively connected by welding to form a spiral shape.

Therefore, in such a device, a plate body in which the tube bodies 1a, lb... are each expanded is cut out from a flat plate material, each plate body is cut out from a flat plate material, and each plate body is cut out from a flat plate material. The bodies have different radii R1 and R2.
. . , and both ends thereof must be successively welded to the outer surfaces of the two speed rings 3 connected to each other by the stay vanes 2.

However, as mentioned above, it takes a lot of time to cut out the expanded plates of each of the tubes 1a and lb and bend the materials to different radii, and the radius of the tubes must be adjusted to a certain tolerance. There are also problems such as it is not always easy to keep it within the limits.

In addition, especially in recent small and medium-sized hydropower plants, many of them have low head or small flow rate, and for power plants with low head,
Even if the cross-sectional shape of the flow path is not circular, it can sufficiently withstand pressure, but on the other hand, for power plants with small flow rates, the radius of the pipe body will be very small, making bending relatively difficult.

In view of these points, it is an object of the present invention to obtain a spiral casing that can maintain the flow path area required for hydraulic design as in the past, and is easy to manufacture. .

[Structure of the invention]

(Means for Solving the Problems) The present invention provides an inner plate that stands upright from a speed ring, an outer plate of a constant height that is disposed outside of the inner plate so as to surround it, and A flow path having a rectangular cross section is formed by the plate and an end plate connecting both ends of the outer plate, respectively, and the outer plate is arranged such that the distance from the central axis of the casing gradually decreases from the inlet side to the end of the winding. It is characterized by its spiral shape.

(Function) As described above, the present invention provides the spiral casing of a water turbine with an inner plate that stands up from the speed ring, an outer plate that is disposed outside of the inner plate, and an end plate that connects the ends of both side plates. A channel with a rectangular cross section is formed by forming a flow path with a rectangular cross section, and only the outer plate is spirally shaped.
Therefore, the inner plate and the end plate need to be flat, and only the outer plate has a spiral shape. There is no need to develop the side plates or bend them to different radii as in the past, which simplifies production. can do.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2.

In FIG. 1, reference numeral 3 denotes a speed ring, and a plurality of stay vanes 2 are arranged circumferentially along the water inflow direction between two speed rings, and the upper and lower ends of each stay vane 2 are connected to the speed ring. It is fixed to ring 3.

Cylindrical inner plates 5 are erected and welded to the outer surfaces of both speed rings 3, respectively. - direction, the above inner plate 5
Outside the inner plate, there is an outer plate 6 which is formed by bending a plate having a constant height H into a spiral shape so that the distance from the central axis C of the casing decreases from the inlet side to the winding end. It is arranged so as to surround 5. Both ends of the inner plate 5 and outer plate 6 are connected by end plates 7, 7, respectively, and the inner plate 5, outer plate 6, and end plate 7 form a casing having a flow path with a rectangular cross section.

Furthermore, as shown in FIG.
is installed.

In the above embodiment, the inner plate 5 is cylindrical, and the outer plate 6 is bent toward the center of the casing. However, as shown by the dashed line in FIG. The inner plate may be made into a regular polygon by sequentially connecting and welding flat plates of appropriate sizes, and the outer plate 6 may be made into a spiral shape.

〔Effect of the invention〕

As explained above, in the present invention, there is an inner plate that stands up from the speed ring, an outer plate of a constant height arranged outside the inner plate, and both ends of the inner plate and the outer plate. A flow path with a rectangular cross section is formed by the end plates connected to each other, and the outer plate is spirally shaped so that the distance from the central axis of the casing or from the inlet side to the end of the winding becomes smaller. The casing can be manufactured very easily by welding flat plates together or by welding a flat plate and a curved plate without the need for unfolding or bending at different radii. Moreover, the flow path area necessary for hydraulic design can be maintained simply by changing the position of the outer plate.

[Brief explanation of drawings]

FIG. 1 is a longitudinal partial view of a spiral casing of the present invention, FIG. 2 is a plan view showing an embodiment of the spiral casing of the present invention, FIG. 3 is a vertical partial view of a conventional spiral casing, and FIG. 4 is a conventional spiral casing. FIG. 3 is a plan view of the spiral casing of FIG. 2... Stay vane, 3... Speed ring, 5... Inner plate, 6... Outer plate, 7... End plate, 8... Reinforcement plate.

Claims (1)

[Claims] An inner plate that stands up from the speed ring, an outer plate of a constant height that is placed outside the inner plate so as to surround it, and an end plate that connects both ends of the inner plate and the outer plate, respectively. A channel with a rectangular cross section is formed by
A spiral casing for a water turbine, characterized in that the outer plate has a spiral shape such that the distance from the central axis of the casing gradually decreases from the inlet side to the winding end.